SETI

The Search for Extraterrestrial Intelligence. The first practical proposals
in SETI were made in the 19th and early 20th centuries, but were aimed only
at interplanetary communication (see communication,
with the Moon and planets). The roots of SETI in its modern form, as
a search for artificial signals over interstellar and even intergalactic
distances, can be traced back to the 1930s with the discovery by Karl Jansky
of radio waves coming from a source
outside the Solar System. This led, in time, to the birth of radio
astronomy and to the construction, in the late 1950s, of the first large
radio telescopes such as those at Jodrell
Bank and Green Bank. Only with such
powerful instruments was it feasible to start looking for Earth-type signals
from nearby stars.

The dawn of SETI

As a serious scientific enterprise, SETI began in 1959 with two independent
events. The first was the publication of a paper in which Cornell researchers
Philip Morrison and Guiseppe Cocconi
discussed the suitability of radio waves
as a communication medium, man's newly-acquired ability to eavesdrop on
interstellar radio conversations, and the optimum frequency at which to
conduct a search (see Morrison and Cocconi Conjecture).
They argued that:

If signals are present, the means of detecting
them is now at hand. Few will deny the profound importance, practical
and philosophical, which the detection of interstellar communications
will have. We therefore feel that a discriminating search for signals
deserves a considerable effort. The probability of success is difficult
to estimate; but if we never search, the chance of success is zero.

Meanwhile, at the National Radio Astronomy Observatory, Green Bank, Frank
Drake had independently arrived at the same
conclusion. Indeed, Drake had already begun to assemble the equipment he
would use in Project Ozma, the first observational
SETI program, carried out in 1960. Despite Ozma's failure to detect any
extraterrestrial transmissions from its two target stars, it served to stimulate
widespread public interest and lively (often critical) scientific debate.
In 1961, an informal conference, sponsored by the Space Science Board, was
held at Green Bank (see Green Bank conference).
A dozen scientists and engineers deeply interested in the possibility of
extraterrestrial life were invited to attend, including Drake himself, Morrison,
Cocconi, Carl Sagan, Su-Shu Huang,
Melvin Calvin, John Lilly,
Bernard Oliver, Dana Atchley,
and J. P. T. Pearman. At the conference, the now famous Drake
Equation was discussed for the first time.

SETI strategies

The dawn of the SETI era stimulated scientists to consider the pros and
cons of searching at all, the best strategy involving radio wave searches,
and alternative approaches to finding evidence of extraterrestrial intelligence.1
Into the last category came the suggestions of Dyson
spheres and Bracewell probes.
The feasibility of interstellar travel was also considered around this time
by Robert Bussard, Freeman Dyson,
Sebastian von Hoerner, John Pierce,
Edward Purcell, and Carl Sagan.

In the Soviet Union, SETI was seen as a natural outcome of communist philosophy
and, partly for this reason, became quickly established as a respectable
field of research. Interest there was initially sparked by the writings
of Iosef Shklovskii and tended to focus on
the possibility of civilizations far in advance of our own. In 1963, a radio
wave search was carried out for Kardashev
civilizations, though at a different frequency to that employed by Project
Ozma.

Within the radio search paradigm, which by the mid-1960s was well-established
as the standard approach to SETI, much debate focused on methodology. An
artificial signal, unlike one of natural origin, would be expected to have
a narrow bandwidth so that it could only
be detected by an antenna tuned to one particular frequency. The question
was which frequency offered the best chance of success. Morrison
and Cocconi had argued for 1,420 MHz, corresponding to the ubiquitous 21-centimeter
line of neutral hydrogen, but the subsequent discovery of other common
natural radio frequencies (see waterhole)
complicated the decision. Moreover, the merits of targeted
searches had to be weighed against those of all-sky
surveys. In the decades following Project Ozma, many different approaches
were tried.

In 1970, NASA,s involvement with SETI began through some preliminary work
carried out by John Billingham. This
led, in 1973, to an ambitious proposal by Billingham and Bernard Oliver,
known as Project Cyclops, to detect extraterrestrial
civilizations by eavesdropping on their stray electromagnetic signals. Although
the proposal failed, it served to stimulate interest in a NASA SETI program
of more modest scale. This eventually led to the High
Resolution Microwave Survey and, when this had to be abandoned because
of budget cuts, its privately-funded successor, Project
Phoenix.

In 1973, what was to become the longest-running SETI program to date, began
at the Ohio State University Radio Observatory.
Its most dramatic moment came in 1977 with the detection of the mysterious
Wow! signal. Meanwhile, Drake and Sagan employed
the giant Arecibo radio telescope to search
for emissions from advanced civilizations in other galaxies. The mid 1970s
also saw the very foundations of SETI challenged by a revival of interest
in the Fermi Paradox.

SETI
today

Today, interest in SETI has never been greater. A number of programs are
active, including the SETI Institute's
Project Phoenix, Harvard's BETA, Berkeley's
SERENDIP, and the SETI
League's Project Argus, this last one
unique in that it relies upon data gathered worldwide by a growing army
of amateur observers. The public's interest in SETI has been heightened
by the suggestion of possible life on Mars
and the giant moons of Jupiter, as well
as by fictional portrayals, such as Sagan's Contact.2
Finally, there is a sense in which SETI, in addition to being a scientific
quest, answers a modern spiritual need (see SETI,
religious dimensions of).

See also SETA (Search for Extraterrestrial Artifacts)
and SETV (Search for Extraterrestrial Visitation)
and the list of SETI observing programs after the references below.2,
3, 4

Introductory paragraph: Since Morrison and Cocconi published
the suggestion that there might be advanced societies elsewhere in
the Galaxy, superior to ourselves in technological development, who
are beaming transmissions at us on a frequency of 1,420 MHz/s., Drake
has described equipment under construction to look for such transmissions.
The confidence necessary to commence actual observations is based
on an opinion that planets are a common by-product of the formation
of starts. One argument among others is that stars of spectral type
later than F5 have low angular momenta, just as the Sun has; and in
the case of the Sun we know that it is because the momentum (98 per
cent of it) resides in planets. Of the thousands of millions of planets
in the Galaxy likely to be situated similarly to the Earth in relation
to their star, it is hard to dismiss the possibility that some have
more advanced civilizations than ours. In view of the acceleration
with which technology develops, advanced societies could be incredibly
more advanced.